In order to approach the characteristics of nitrogen and phosphorus pollution caused by cage culture and the balance of nitrogen and phosphorus during the process of cage culture, a monitoring was conducted in Daya Ba...In order to approach the characteristics of nitrogen and phosphorus pollution caused by cage culture and the balance of nitrogen and phosphorus during the process of cage culture, a monitoring was conducted in Daya Bay of Guangdong Province, China from April 2002 to Jane 2003. The results show that the concentrations of total nitrogen （TN） in the waters at the sites with five and ten years of cage culture history are 1.8 and 2.3 times of that at control site respectively. Ammonium （NH3-N） is the main form of nitrogen in spring while nitrate （NO~） in winter. The concentrations of TN, total dissolved nitrogen （TDN） and dissolved organic nitrogen （DON） are highest in autumn. The concentration of phosphorus increases with the increasing of the culturing time, among which phosphate （ PO^-34） increases most obviously. The concentrations of total phosphorus （TP） and total dissolved phosphorus （TDP） are highest in autumn. The nitrogen and phosphorus are accumulated significantly in the sediment of cage culture area. The model of N balance in the cage culture area： bait （70.62%） ＋ fry （0.28%） ＋ input by tide （14.8%） ＋ release from sediment 04.3%） = harvest of adult fish （12.07%） ＋ deposition into sediment （28.75%） ＋ output by tide （56.18%） ＋ others （3.00%）. The model of P balance： bait （83.11%） ＋ fry （0.17%） ＋ input by tide （12.23%） ＋ release from sediment （4.49%） = harvest of adult fish （8.43%） ＋ deposition into sediment （48.59%） ＋ output by tide （41.94%） ＋ others （1.04%）. In one fish growth year, the contents of nitrogen and phosphorus in harvest of adult fish are only 17.0% and 10.1% of the contents of nitrogen and phosphorus in fish bait and fry, wherein 83% of nitrogen and more than 89% of phosphorus in fish bait became marine pollutants.展开更多
Impact of LaMmichthys crocea cage culture in Daiqu fishery （Zhoushan, Zhejiang Province） on the chemistry of the sediment was inves- tigated. Sediment samples, in different depths and from three stations at various ...Impact of LaMmichthys crocea cage culture in Daiqu fishery （Zhoushan, Zhejiang Province） on the chemistry of the sediment was inves- tigated. Sediment samples, in different depths and from three stations at various distances from the cage, were collected, for analyzing total organic matter, total organic carbon, total nitrogen and phosphorus. The results showed a significant increase in all analyzed parameters in station 1, at 5 m from the cage. The difference between reference station （600 m from the cage） and station 2 at 95 m to the cage was insignificant, indicating lo- calized impact of cage farming to the vicinity of cage. The analyzed parameters in various depths did not show a significant difference. The values of analyzed parameters in the perimeter of the cage and their differences with reference stations showed small magnitude and localized impact on the chemistry of sediment. It might be because of deep water and moderate velocity of water current in this fjord. The magnitude of impact may dif- fer durina the summer when biomass and feedina rate would be at the maximum level.展开更多
This research was conducted in Gokcekaya Reservoir, which is located on the Sakarya River (Ankara, Turkey). Sediment samples were obtained before and after culture periods at a rainbow trout (Oncorhynchus mykiss) farm...This research was conducted in Gokcekaya Reservoir, which is located on the Sakarya River (Ankara, Turkey). Sediment samples were obtained before and after culture periods at a rainbow trout (Oncorhynchus mykiss) farm with a capacity of 950 t·y-1. Total phosphorus (TP: 8.80 ± 0.50 and 9.10% ± 0.20%), total nitrogen (TN: 17.0 ± 0.20 and 17.05% ± 0.10%), organic matter (OM: 14.40 ± 0.40 and 14.60% ± 0.20%), redox potential (327.00 ± 0.08 and 170.00 ± 4.08 mV), water content (97.68 ± 0.28 and 96.38% ± 0.41%) and total organic carbon (TOC: 11.30 ± 0.10 and 13.40% ± 0.10%) were measured before and after the culture period, respectively. The mean rank order of sediment heavy metal was evaluated as Fe > Mn > Ni > Zn > Cr > Cu. The soluble reactive phosphorus (SRP) concentrations in the sediment pore water were 2.52 ± 0.14 and 7.75 ± 1.18 μg·L-1;ammonium (NH3) was measured as 1.13 ± 0.09 and 1.18 ± 0.06 μg·L-1;nitrite (NO2) was 8.83 ± 0.23, 12.75 ± 0.22 μg·L-1;nitrate (NO3) was elevated at 0.14 ± 0.07 and 0.24 ± 0.02 μg·L-1, and positive phosphorus release remained at low levels: 3.35 μg·m-2d-1 (before the culture period, September 2011) and 11.04 μg·m-2d-1 (after the culture period, April 2012). The data on the sediment and the sediment pore water of the rainbow trout culture in Gokcekaya Reservoir shows that the cage culture in its present condition has no negative effect on sediment quality.展开更多
The objective of the study was to determine the optimal density of fingerlings of the Nile tilapia (<em>Oreochromis niloticus</em>) culture in floating cages with respect to growth performance and to know ...The objective of the study was to determine the optimal density of fingerlings of the Nile tilapia (<em>Oreochromis niloticus</em>) culture in floating cages with respect to growth performance and to know the effect of temperature on growth during the winter period. Tilapia fingerlings (mean weight 8.5 ± 0.36 g) were stocked at densities of 120, 180 and 360 fish/m<sup>3</sup> for 10 weeks. During culture, fish were fed a diet contains 35% protein made of peanut seed, cottonseed, wheat bran, and Sorghum. The results showed that the increase in fish density reduced the final weight of the fish. The percentage of the fish weight increased and reached 111% ± 1.45% in the lowest fish density (120 fish/m<sup>3</sup>), 79% ± 1.87% in the medium density (240 fish/m<sup>3</sup>), and 63% ± 2.03% of high fish density (360 fish/m<sup>3</sup>), therefore the daily growth rate was better in the lowest density. The rate of food conversion ratio was also better in the lowest density with 2.17 ± 0.33, followed by the medium density with 2.79 ± 0.28 and then the highest density with 3.09 ± 0.21. However, the total production in the cage increased with increasing fish density, and the return to the cost of food was better with higher fish density. According to various performance evaluation criteria, it can be concluded that the medium density 240 fish/m<sup>3</sup> is the best for growing Nile tilapia fingerlings in floating cages. It was observed that the growth rates of the three treatments were low due to the decrease in water temperature in most of the study period, which may indicate the useless of culture in cages in the winter season.展开更多
基金Under the auspices of National Natural Science Foundation of China (No. 40071074)Scientific Technology Research and Development Foundation of Environmental Protection Agency of Guangdong Province (No. 20002026242402)
文摘In order to approach the characteristics of nitrogen and phosphorus pollution caused by cage culture and the balance of nitrogen and phosphorus during the process of cage culture, a monitoring was conducted in Daya Bay of Guangdong Province, China from April 2002 to Jane 2003. The results show that the concentrations of total nitrogen （TN） in the waters at the sites with five and ten years of cage culture history are 1.8 and 2.3 times of that at control site respectively. Ammonium （NH3-N） is the main form of nitrogen in spring while nitrate （NO~） in winter. The concentrations of TN, total dissolved nitrogen （TDN） and dissolved organic nitrogen （DON） are highest in autumn. The concentration of phosphorus increases with the increasing of the culturing time, among which phosphate （ PO^-34） increases most obviously. The concentrations of total phosphorus （TP） and total dissolved phosphorus （TDP） are highest in autumn. The nitrogen and phosphorus are accumulated significantly in the sediment of cage culture area. The model of N balance in the cage culture area： bait （70.62%） ＋ fry （0.28%） ＋ input by tide （14.8%） ＋ release from sediment 04.3%） = harvest of adult fish （12.07%） ＋ deposition into sediment （28.75%） ＋ output by tide （56.18%） ＋ others （3.00%）. The model of P balance： bait （83.11%） ＋ fry （0.17%） ＋ input by tide （12.23%） ＋ release from sediment （4.49%） = harvest of adult fish （8.43%） ＋ deposition into sediment （48.59%） ＋ output by tide （41.94%） ＋ others （1.04%）. In one fish growth year, the contents of nitrogen and phosphorus in harvest of adult fish are only 17.0% and 10.1% of the contents of nitrogen and phosphorus in fish bait and fry, wherein 83% of nitrogen and more than 89% of phosphorus in fish bait became marine pollutants.
基金Supported by Zhejiang Provincial Natural Science Foundation of China(LQ13D060001,LY14D060003)
文摘Impact of LaMmichthys crocea cage culture in Daiqu fishery （Zhoushan, Zhejiang Province） on the chemistry of the sediment was inves- tigated. Sediment samples, in different depths and from three stations at various distances from the cage, were collected, for analyzing total organic matter, total organic carbon, total nitrogen and phosphorus. The results showed a significant increase in all analyzed parameters in station 1, at 5 m from the cage. The difference between reference station （600 m from the cage） and station 2 at 95 m to the cage was insignificant, indicating lo- calized impact of cage farming to the vicinity of cage. The analyzed parameters in various depths did not show a significant difference. The values of analyzed parameters in the perimeter of the cage and their differences with reference stations showed small magnitude and localized impact on the chemistry of sediment. It might be because of deep water and moderate velocity of water current in this fjord. The magnitude of impact may dif- fer durina the summer when biomass and feedina rate would be at the maximum level.
文摘This research was conducted in Gokcekaya Reservoir, which is located on the Sakarya River (Ankara, Turkey). Sediment samples were obtained before and after culture periods at a rainbow trout (Oncorhynchus mykiss) farm with a capacity of 950 t·y-1. Total phosphorus (TP: 8.80 ± 0.50 and 9.10% ± 0.20%), total nitrogen (TN: 17.0 ± 0.20 and 17.05% ± 0.10%), organic matter (OM: 14.40 ± 0.40 and 14.60% ± 0.20%), redox potential (327.00 ± 0.08 and 170.00 ± 4.08 mV), water content (97.68 ± 0.28 and 96.38% ± 0.41%) and total organic carbon (TOC: 11.30 ± 0.10 and 13.40% ± 0.10%) were measured before and after the culture period, respectively. The mean rank order of sediment heavy metal was evaluated as Fe > Mn > Ni > Zn > Cr > Cu. The soluble reactive phosphorus (SRP) concentrations in the sediment pore water were 2.52 ± 0.14 and 7.75 ± 1.18 μg·L-1;ammonium (NH3) was measured as 1.13 ± 0.09 and 1.18 ± 0.06 μg·L-1;nitrite (NO2) was 8.83 ± 0.23, 12.75 ± 0.22 μg·L-1;nitrate (NO3) was elevated at 0.14 ± 0.07 and 0.24 ± 0.02 μg·L-1, and positive phosphorus release remained at low levels: 3.35 μg·m-2d-1 (before the culture period, September 2011) and 11.04 μg·m-2d-1 (after the culture period, April 2012). The data on the sediment and the sediment pore water of the rainbow trout culture in Gokcekaya Reservoir shows that the cage culture in its present condition has no negative effect on sediment quality.
文摘The objective of the study was to determine the optimal density of fingerlings of the Nile tilapia (<em>Oreochromis niloticus</em>) culture in floating cages with respect to growth performance and to know the effect of temperature on growth during the winter period. Tilapia fingerlings (mean weight 8.5 ± 0.36 g) were stocked at densities of 120, 180 and 360 fish/m<sup>3</sup> for 10 weeks. During culture, fish were fed a diet contains 35% protein made of peanut seed, cottonseed, wheat bran, and Sorghum. The results showed that the increase in fish density reduced the final weight of the fish. The percentage of the fish weight increased and reached 111% ± 1.45% in the lowest fish density (120 fish/m<sup>3</sup>), 79% ± 1.87% in the medium density (240 fish/m<sup>3</sup>), and 63% ± 2.03% of high fish density (360 fish/m<sup>3</sup>), therefore the daily growth rate was better in the lowest density. The rate of food conversion ratio was also better in the lowest density with 2.17 ± 0.33, followed by the medium density with 2.79 ± 0.28 and then the highest density with 3.09 ± 0.21. However, the total production in the cage increased with increasing fish density, and the return to the cost of food was better with higher fish density. According to various performance evaluation criteria, it can be concluded that the medium density 240 fish/m<sup>3</sup> is the best for growing Nile tilapia fingerlings in floating cages. It was observed that the growth rates of the three treatments were low due to the decrease in water temperature in most of the study period, which may indicate the useless of culture in cages in the winter season.
